1. Field of the Invention
The present invention relates to a method of fabricating a display device, and particularly, to a method of fabricating a liquid crystal display device.
2. Description of the Related Art
As portable electric devices, such as mobile phones, personal digital assistants, and notebook computers, are being developed, requirements for flat panel display devices having lightweight and thin profiles are increasing. Among these flat panel display devices, such as liquid crystal displays (LCDs), plasma display panels (PDPs), field emission displays (FEDs), and vacuum fluorescent displays (VFDs), the LCDs are desirable due to their ability to be mass produced, their easy driving means, and their realization of high quality images.
FIG. 1 is a cross sectional view of a liquid crystal display device according to the related art. In FIG. 1, a liquid crystal display device 1 includes a lower substrate 5 (i.e., a driving device array substrate), an upper substrate 3 (i.e., a color filter substrate), and a liquid crystal layer 7 formed between the lower and upper substrates 5 and 3. Although not shown, a plurality of pixels are formed on the lower substrate 5, a driving device, such as a thin film transistor, is formed on each of the pixels, and a color filter layer is formed on the upper substrate 3 for producing colored images. In addition, a pixel electrode (not shown) and a common electrode (not shown) are formed on the lower substrate 5 and the upper substrate 3, respectively, and an alignment layer (not shown) for orienting liquid crystal molecules of the liquid crystal layer 7 is applied thereon.
The lower substrate 5 and the upper substrate 3 are attached together using a sealing material 9, wherein the liquid crystal layer 7 formed therebetween. Accordingly, by driving liquid crystal molecules using the driving device formed on the lower substrate 5, light passing through the liquid crystal layer 7 is controlled. Thus, images are displayed.
FIG. 2 is a flow chart of a method of fabricating a liquid crystal display device according to the related art. In FIG. 2, a method of fabricating the liquid crystal display device can be divided into a driving device array substrate process for forming the driving device on a lower substrate, a color filter substrate process for forming a color filter on an upper substrate, and a cell process for forming display cells.
A step S101 (TFT array process) includes forming a plurality of gate lines and data lines on the lower substrate to define pixel areas and forming a thin film transistor at each of the pixel areas. Accordingly, the TFT is driven by signals transmitted along the gate and data lines. In addition, the pixel electrode is formed during the driving device array process.
A step S104 (color filter process) includes forming color filter layer of R, G, and B colors and a common electrode on the upper substrate.
Steps S102 and S105 (applying and rubbing alignment layer) include applying alignment layers on both the upper substrate and the lower substrate, and rubbing the alignment layers to provide the liquid crystal molecules of the liquid crystal layer formed between the upper and lower substrates with an anchoring force or a surface fixing force (i.e., pre-tilt angle and orientation direction).
Step S103 (scattering spacer) includes providing spacers on the lower substrate 5 to maintain a constant cell gap between the upper and lower substrates.
Step S106 (applying sealing material) includes applying a sealing material along an outer perimeter of the upper substrate.
Step S107 (attaching) includes attaching the upper substrate and the lower substrate together by compressing the upper and lower substrates together.
Step S108 (fabricating) includes dividing (i.e., cutting) the attached upper and lower substrates into single liquid crystal display panels.
Step S109 (liquid crystal injection and sealing) includes injecting liquid crystal into each of the single liquid crystal panels through a liquid crystal injecting hole, and sealing the liquid crystal injecting hole.
Step S110 (test) includes examining each of the liquid crystal panels for defects.
FIG. 3 is a schematic view of a liquid crystal injection system according to the related art. In FIG. 3, nitrogen (N2) gas is supplied into a vacuum chamber 10 when an injection hole 16 of liquid crystal panel 1 contacts liquid crystal 14 in a container 12. Then, pressure within the vacuum chamber 10 is reduced and the liquid crystal is injected into the liquid crystal panel 1 through the injection hole 16 due to a difference between the pressure inside the liquid crystal panel 1 and the vacuum chamber 10. In addition, the injection hole 16 is completely sealed by a sealing material after filling of the liquid crystal into the liquid crystal panel 1. Accordingly, a liquid crystal layer is formed between upper and lower substrates of the liquid crystal panel 1.
However, since the liquid crystal is injected through the injection hole 16 of the liquid crystal panel 1 due to pressure differences between the liquid crystal panel 1 and the vacuum chamber 10, it takes a long time to inject the liquid crystal. Since a gap between the lower substrate (i.e., driving device array substrate) and the upper substrate (i.e., color filter substrate) of the liquid crystal panel 1 is very narrow, (i.e., a few μm), only a small amount of liquid crystal can be injected into the liquid crystal panel 1 per unit time. For example, it takes about 8 hours to completely inject the liquid crystal into a liquid crystal panel having sides of about 15 inches. Thus, total fabrication time of the liquid crystal panel 1 increases due to the liquid crystal injection.